Various types of downhole drilling tools including, but not limited to, rotary drill bits, reamers, core bits, and other downhole tools have been used to form wellbores in associated downhole formations. Examples of such rotary drill bits include, but are not limited to, fixed cutter drill bits, drag bits, PDC drill bits, and matrix drill bits associated with forming oil and gas wells extending through one or more downhole formations.
Various techniques and procedures have been used to stabilize such downhole drilling tools and improve their drilling performance. See for example: Brett J. F., Warren T. M. and Behr S. M., “Bit Whirl: A new Theory of PDC bit Failure”, SPE 19571, October, 1989; Warren T. M, Brett J. F. and Sinor L. A., “Development of a Whirl—Resistant Bit”, SPE Drilling Engineering, 5 (1990) 267-274; Weaver G. E., Clayton R., “A New PDC Cutting Structure Improves Bit Stabilization and Extends Application into Harder Rock Types”, SPE/IADC 25734, 1993; Besson A., et al., “On the Cutting Edge”, Oilfield Review, Autumn, 2000, p 36-57; and TransFormation Bits, ReedHycalog, 2004.
Placement of different types of cutting elements in different bit profile zones of a drill bit has been used to improve performance. For example, U.S. Pat. No. 5,787,022 describes placing different types of cutters on various regions (zones) of a bit face to accommodate anticipated mechanical loadings. U.S. Pat. No. 6,435,058 describes layout of at least two types of cutters with different abrasion resistance based on the wear rate of cutters along the bit profile. U.S. Pat. No. 6,481,511 describes placing cutters in a series of concentric rings (zones) wherein cutters in each concentric ring have a respective wear resistance and that the wear resistance of cutters in different concentric rings are different. According to these previous methods at least two different types of cutters may be placed on each blade. However, placing different types of cutters in different bit profile zones may lead to catastrophic cutter failure and/or create “ring out” at those zones with lower abrasion resistance cutters. The “ring out” on bit face may be easily created at the transition between two zones. Once “ring out” is created, bit performance may be significantly reduced. Therefore, there is still a need for downhole drilling tools having different types of cutters that can better withstand impact loadings and resist wear and reduce cost without sacrificing bit performance.